One hazard of operating small watercraft such as motor boats is that the operator may be knocked overboard while the craft is in operation. After falling overboard, the hull or propeller of the craft may strike and injure the operator. In addition, the craft may continue to run after the operator falls overboard, making it difficult for the operator to retrieve the boat and return safely to shore.
It has been proposed to reduce the hazard of falling overboard by providing an electrical cut-off switch which disabled the motor if the operator was ejected from the craft. According to one such proposal, the cut-off switch took the form of a push button switch. A lanyard was coupled at one end to the operator and was clipped or tied at the other end to a stem below the actuating surface of the push button switch. When the lanyard was engaged with the cut-off switch, the motor was enabled to operate. If the operator then fell overboard, the lanyard pulled loose from the switch so that the switch disabled the motor. After the lanyard has been pulled loose, the operator might restart the motor by depressing the push button switch.
One drawback to this proposal was that the push button cut-off switch provided no security against unauthorized operation of the boat. Furthermore, the cut-off switch made no provision for energizing a starter solenoid when the motor was started. This required that other electrical switches be provided on the motor to facilitate starting. These other switches increased the cost of the motor as well as the likelihood of a failure of the motor's electrical system.